JPS58136626A - Polycarbosilane partially containing siloxane bond - Google Patents

Abstract

PURPOSE:The titled polycarbosilane being excellent in heat and oxidation resistance and generating much burning residue in a non-oxidizing atmosphere, prepared by polymerizing a mixture of a specified polysilane and a polyborosilane containing phenyl groups in at least part of the Si side chains. CONSTITUTION:A polysilane of formulaI(wherein R1 and R2 are each H, CH3, C2H5 or C6H5 and n >=3) is mixed with 0.01-15wt% polyborosilane, number- average MW of 500-10,000, which has skeletal components containing B, Si and O, and has phenyl groups on at least part of the Si side chains, and the mixture is polymerized at 250-500 deg.C for 3-10hr in an atmosphere inert to the reactions to obtain a polycarbosilane partially containing siloxane bonds, comprising structural units of formulas II and III (wherein R3 and R4 are each R1) and having a ratio of formula II/formula III of 5-200:1, a number-average MW of 500-10,000, and an intrinsic viscosity of 0.01-1.50.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel polycarbosilane compound containing a siloxane bond as a part thereof.

This polymer is converted into inorganic carbide SiC by firing, so it is used as a raw material for SiC, such as SiC fibers, films, coatings, sintering binders, impregnating agents, It is used as SiC powder.

In addition, various uses of the polymer itself have been affected.

There are two types of conventionally known polycarbosilanes: polycarbosilane obtained by in-it polymerization of monosilane, and polycarbo7lane obtained by converting monosilane into -H polysilane and then polymerizing this. The former is Fr
1tz;Angew, Chem.

79p, 657 (1967), etc., and the latter can be produced by the method disclosed by the present inventors in JP-A No. 52
-74000 and JP-A-52-112700. However, in order to obtain polycal silane, which has excellent heat resistance and oxidation resistance and has a high firing residue rate in a non-oxidizing atmosphere, using conventional manufacturing methods, it is necessary to use a pressurized container such as an autoclave or to recycle it. It was necessary to use a flow-through device that could be used. In the former method of polymerization using a pressurized container, for example, using a tube such as an autoclave,
It is necessary to heat it to a temperature of 470°C and carry out a reaction for 10 to 15 hours under a pressure of 80 to 110 atm, which requires pressure-resistant equipment and disaster prevention measures, and it has the disadvantage that VcFi is not suitable for mass production. . In addition, in the latter method of polymerization using a flow-type device that can be recycled, the low molecular weight components produced are separated in a device equipped with IJI equipment such as a heating reaction tower and a product separation tower, and this is forcedly circulated. Because the reaction must be repeated in a heated reaction tower, the
There are many industrial disadvantages, such as the need for heating to a high temperature of ~800°C and the long reaction time of 20 to 50 hours.

The present inventors have conducted extensive research to overcome the above-mentioned drawbacks of conventional methods, and have found that there is no need to use any special equipment such as a pressurized container or a flow-through device, and the method can be used at relatively low heating temperatures. A new and advantageous production method has been discovered that allows polycarbosilane to be obtained in a short time. Furthermore, the present inventors have found that the polycarbosilane obtained by the above method has better heat resistance and oxidation resistance than the polycarbosilane obtained by the Kairai method, and it is easier to sinter in a non-oxidizing atmosphere. It has been discovered that this is a new polycarbosilane with excellent performance and a high residual rate.

2 (n≧3, RI and R2 each independently represent CH3, C2H5, C6H, or H), the skeleton consists of B, Si, and O, and at least one of the Si side chains A siloxane bond characterized in that 0.01-15% by weight of polyborosiloxane having a phenyl group is added and mixed, and the mixture of the polymers is heated and polymerized in an atmosphere inert to the reaction. A method for producing a polycarbosilane containing a portion of is provided.

The polycarbosilane of the present invention obtained by the above method mainly consists of the following structural units (A) and l), (A): RI-8i-CH2-2<B):'Rsl5i-0- 4 (RIXR2, R3 and R4 are each independently CH3,
The ratio of C2H6, C6B, which still represents H) (A) and l) is 5:1 to 200:1, and the number average molecular weight is 5.
00-10,000, intrinsic viscosity is 0. It is a polycarbosilane containing a portion of a polycarbosilane bond, which is characterized by having an O1 to 1.50, excellent heat resistance and oxidation resistance, and a high firing residue rate in a non-oxidizing atmosphere.

The present invention will be explained in more detail below.

2 to C2, C6μ6, H), and the +19 structure of this polysilane may be either linear or cyclic, or it may be a mixture of these two types of structures. In the above formula, n>3, preferably 5<:n<100. Side chain R8, R2, R3
and R4 each independently represent a methyl group, an ethyl group, a phenyl group, or hydrogen, that is, R and R2 bonded to each Si atom forming the skeleton of the polysilane may be the same or different from each other, When the side chains of the polysilane are composed of two or more types of methyl, ethyl, phenyl and hydrogen, the different side chains in the polysilane may be arranged in any order.

A particularly suitable polysilane for OH3 used as a starting material in the method of the present invention is a polysilane having only -8i- as a single, IOH3-position structure, or a polysilane in which 50 or more of the side chains are methyl groups. It is a polysilane in which the remaining side chains are a phenyl group and/or hydrogen.

In the case of linear polysilane, the terminal group is preferably OH or CH3.

The polysilane used in the present invention is, for example, published in "Chemistry of Organosilicon Compounds" co-authored by Ishide et al., Kagaku Dojinsha (1972).
Although it can be synthesized by various methods such as those described in et al., it is usually produced by dechlorinating one or more dichlorosilanes with sodium. The dechlorination reaction of one type of dichlorosilane is expressed as follows.

RR Another starting material W used in the method of the present invention is a polysiloxane (hereinafter simply phenyl The group-containing poly (sometimes referred to as rosiloxane) is disclosed in Japanese Patent Application Laid-open No. 53-42300 and No. 53-50299, for which the present inventors previously filed patent applications.
For example, boric acid and one or more diorganodichlorosilanes (if at least a portion of the organo groups of the diorganodichlorosilanes are It is produced by dehydrochloric acid condensation reaction with phenyl group). To illustrate how the condensation reaction proceeds in this case, take the reaction of diphenyldichlorosilane and boric acid as an example.
The main reactions are thought to be as follows.

C, H.

Police C@M.

Preferred diorganodichlorosilanes used when the phenyl group-containing poly, which is the starting material for the method of the present invention, is produced by the above reaction are zophenyl V chlorosilane and/or hamethylphenyl V chlorosilane. , or a mixture of these with methyldichlorosilane.

In addition to the hydrochloric acid condensation reaction used as one of the starting materials in the method of the present invention, for example, the dealcoholization condensation reaction of boric acid and one or more diorganodialkoxysilanes, and the Deesterification condensation reaction between boric acid sweat stellate and diorganodialkoxysilane (
However, at least some of the organo groups in the diorganodialkoxysilane used in these reactions are phenyl groups)
It can also be manufactured by

Since the condensation reaction in the above production method is quite complex, it is necessary to completely elucidate the structure of the condensation reaction product, phenyl group-containing polyborosiloxane. In the phenyl group-containing polyborosiloxane used as a starting material in the method of the present invention, at least some of R5 and R4 in at least some of the structural units in the polymer are composed of phenyl groups. Without it (there is no phrase.

The preferred polyborosiloxane is a 4-unit lower alkyl group in which all the side chains bonded to Si present in the polymer are phenyl groups, and the remaining side chains are methyl groups;
or a polyborosiloxane such as hydrogen.

Examples of diphenyl-containing polyborosiloxanes used in the present invention are shown below, but these are provided to facilitate understanding of the present invention, and are not intended to limit the present invention.

In addition to polyborosiloxanes having linear, branched or cyclic structures as shown above, polyborosiloxanes having complex structures in which these are further crosslinked are also included in the diphenyl-containing polyborosiloxanes used in the present invention. be done.

The phenyl group-containing polyborosiloxane used as a starting material in the present invention usually has a number average molecular weight of 500 to 10,0.
00, and is characterized by excellent resistance to hydrolysis and heat resistance. For example, polyborodiphenylsiloxane with a molecular weight of 2350 has a molecular temperature of 800'O.
R1 In the method of the present invention, at least one of the polysilanes having the structural unit ±Si+n,
The phenyl group-containing polyborosiloxane is 0.01-1
5% by weight was added and mixed, and the mixture was heated and polymerized in an atmosphere inert to the reaction.

A special device is not required as a matching device; for example, a simple device as shown in FIG. 1 can be used.

In FIG. 1, α is a heating furnace such as a normal electric furnace, b is a reflux device made of hard glass and uses cooling water, and C is a can-shaped reaction vessel made of, for example, quartz or stainless steel. d.

is the inlet of the gas inert to the reaction, and d is its outlet.

That is, in the production method of the present invention, it is possible to synthesize sufficiently excellent polycarbosilane by using a simple heating furnace, reaction vessel, reflux equipment, etc. It is not necessary to use special equipment such as pressurized containers or recyclable flow-through equipment as in the manufacturing method of .

In the method of the present invention, it is necessary to carry out the polymerization reaction by heating under a gas atmosphere inert to the reaction. If the polymerization reaction is carried out in an oxidizing atmosphere such as air, the raw material polysilane will be oxidized and the reaction will not proceed sufficiently, which is not preferable. Nitrogen, argon, and hydrogen are particularly suitable as the gas inert to the reaction.

In addition, it is generally preferable to carry out the polymerization reaction near normal pressure. If the polymerization reaction is carried out in a vacuum or under high or reduced pressure, the produced low molecular weight components will be distilled out of the system, resulting in a significant decrease in yield, so it is preferable. do not have. In order to carry out the method of the present invention, it is preferable to carry out the polymerization reaction while feeding an inert gas into the reaction section as a gas stream. This is because it is possible to prevent temperature rise and pressure rise due to gases such as methane released during the reaction.

The heating temperature in the method of the present invention is lower than that in conventional methods, usually 250°C or higher, preferably 800 to 50°C.
0C is one of the advantages of the method of the invention. If the reaction temperature is below 250C, polymerization will be difficult to proceed;
If the temperature is above .degree. C., mineralization of the produced polycarbosilane, that is, scattering of the side chain components, begins gradually, which is not preferable.

Another important advantage of the present invention is that the thermal polymerization in the method of the present invention is usually completed in a relatively short time, such as 3 to 10 hours. No substantial improvement is observed in the polycarbosilane obtained even after heating for more than 10 hours.

The polycarbosilane obtained by the above polymerization reaction can be purified by dissolving it in a solvent, filtering it, and then evaporating the solvent. If necessary, 50-450'O
The average molecular weight can be increased by distilling and concentrating under normal pressure or reduced pressure within a temperature range of . Examples of such solvents include normal hexane, benzene, quinolene, and tetrahydrofuran.

The novel feature of the process of the invention is that polycarbosilanes are produced from mixtures of polysilanes with the addition of small amounts of phenyl-containing polyborosiloxanes. It is believed that the adoption of such a new starting material brings about the advantages of the method of the present invention, namely, no special reaction equipment is required, the heating temperature is relatively low, and the heating time is short. It will be done. Below, we will discuss the mechanism of why the above advantages are brought about by adding a small amount of phenyl group-containing polyborosiloxane to polysilane, but this is just one speculation. This theory does not limit the present invention in any way.

One starting material for the process of the invention, boria, is pyrolyzed. The result is a low molecular weight product consisting of low molecular weight polysilas or mixtures thereof. When the temperature further increases to 200 to aOOC, partial thermal cleavage of the B-0 bond of the phenyl group-containing polyborosiloxane occurs, and the low molecular weight product binds to the cleaved portion to form an intermediate product. . The formation of this intermediate product is selective for lower molecular weight products in order to reduce steric hindrance, but since it is thermally unstable, the heating temperature is further increased to 250~250°C.
500'C! In the process of promoting stable -8i-CH,,- bonds, boron is decomposed and released from the reaction system as low-boiling alkylboron (R-B-R) or boron hydride. It is thought that it will be released. However, according to polymerization (KPjAl), there is a possibility that a small amount of boron remains in the polycarbosilane with a B-0-8i bond.

By the way, when only polysilane is used as a starting material, the low molecular weight products generated by its thermal decomposition are easily released outside the reaction system, so the polymerization reaction may not be carried out in terms of yield. In order to prevent scattering of low molecular weight products, special equipment such as a pressurized closed container or a flow system for recycling low molecular weight components and gradually converting them into polymers is required.

However, when following the method of the present invention and using a mixture of polysilane and polyborosiloxane as a starting material, as explained above, the B-0
Since the low molecular weight products generated by thermal decomposition of polysilane are captured at the bond cutting site, it is possible to effectively prevent the low molecular weight products from escaping out of the reaction system. Moreover, since polyborosiloxane exhibits a kind of catalytic effect on the reaction, in the method of the present invention, an open reaction vessel is used at normal pressure without using a pressurized sealed vessel or special recycling equipment. Even if the reaction is carried out at a relatively low temperature, it is possible to carry out the polymerization reaction smoothly and in high yield, and as a result, a polycarbonane containing a 5i-0 bond as a part of the polymer skeleton can be obtained.

In the method of the present invention, the amount of polyborosiloxane added is 0.01 to 15% by weight relative to polysilane. The reason for this is that if the amount is less than 0.01%, the above-mentioned effect of trapping the low molecular weight components will not be sufficiently achieved, and the amount of low molecular weight components released will increase, resulting in poor reaction yield.On the other hand, if more than 15% by weight is added, , 5i-0 in the obtained polycarbosilane
This is because the increase in the bonding ratio impairs the original properties and usefulness of polycarbosilane, which is undesirable.

Suitable amounts of polyborosiloxane added range from 0.05 to 10% by weight.

The polymerization reaction in the method of the present invention proceeds by heating alone, but if desired, a polymerization method by adding a radical initiator such as be/diyl peroxide or a catalyst containing aluminum or boron, or a polymerization method by irradiation can be used. etc. can also be used together.

Next, the polycarbosilane partially containing siloxane bonds of the present invention obtained by the above production method will be explained. Poly7 polycarpo7 run J as the starting material polysilane
For example, as shown in -, the R absorption spectrum has a wave number of 800.
5i-CH3 near crn-' and 1250 m-1;
C-H of 1400.2900.2950 cm −'
; 5z-H at 2100 cm-'; 1020.1855
5i-CH2-8i of m-'; l 050cm-'
Nearby 5i-Cj;'too, 1120.1480cr
It shows the absorption based on each bond of S i -C6H and H of n-'. However, B- of the wave number 1840cr++-'
0-(Si) or 8220crn-' B-O
Absorption due to H is usually not detected, so the presence of B-0 bonds in polycarbosilanes is unknown depending on the IR spectra.

In addition, by measuring the ultraviolet absorption spectrum, -8i-
It was confirmed that the 8i-component had almost disappeared.

The elemental ratio according to chemical analysis is generally Si: 80-60, C
: 20-60, O: o, s-5, H: 5-10.

From the results of the above-mentioned IR spectrum, ultraviolet navy absorption spectrum, and chemical analysis, the following conclusions can be drawn regarding the +h structure of the polycarbosilane partially containing siloxane bonds of the present invention. That is, from the measurement results of the JR spectrum, there are 1 elements constituting the polycarbosilane, and from the measurement results of the ultraviolet absorption spectrum, there are 1 elements, so the polycarbosilane of the present invention has substantially the following structural units: <A> and (B).

(A):R.

-8i-CH2-2 (B): R3 -8i -0-4 (However, R8, R2, R3 and R4 are CH5, C
Furthermore, the ratio of the structural units of (A) and (Z?) is 5:1 to 200:1 from the results of chemical analysis of the element ratios.

As a result, the decomposition of polyborosiloxane occurs through Si+O-B bonds, so structural unit 1) is randomly distributed in polycarbosilane, and the phenyl group that was present as a side chain of Si in polyborosiloxane is It is assumed that it will remain as is.

From the above, in the method of the present invention, the structure of the polycarbosilane obtained when poly/methylsilane and polyboro/phenylsiloxane are used as starting materials is as follows:
It can be estimated as follows.

The polycarbo-7 run of the present invention has a number average molecular weight of 500 to IO,000 as measured by vapor pressure osmosis, and an intrinsic viscosity of o,oi to 1.50.

The polycarbosilane containing siloxane bonds of the present invention has a higher decomposition temperature (that is, improved heat resistance), excellent oxidation resistance, and a lower firing residue rate than polycarbosilane produced by conventional methods. It has an excellent characteristic of being large.

This fact is clear from the practical results shown in Table 1 below. 1%
, Table 1 shows polycarbosilane synthesized from polymethylsilane using a conventional method in a pressurized container (autoclave) at a final pressure of 110 atm in an argon atmosphere container for 14 hours at 470°C, and this polycarbosilane. 3. Polydimethylsilane and polydimethylsilane at 400°C for 5 hours in a nitrogen stream by the method of the invention.
Comparison of properties with polycarbonane containing siloxane bonds synthesized from 85 weight i% of polyborodiphenylsiloxane is shown.

The polycarbosilane of the present invention is a thermoplastic material that melts by heating between 50 and 800'0, and still contains benzene,
Since it is soluble in solvents such as n-hexane, xylene, and tetrahydrofuran, it can be made into molded bodies with various shapes, which are heated and fired at temperatures of 700°C or higher to mainly form Kabuki carbide SiC molded bodies. It can be converted.

Examples of such fibers include continuous fibers, fibers, lumes, Fbl&, powders, etc. mainly made of silicon carbide. The polycarbosilane of the present invention has a high firing residual rate, so it is an extremely advantageous polymer because the yield when obtaining these SiC'g14 products is high. In addition to the above-mentioned SiC products, the polycarbonate of the present invention can also be used as a sintering binder and an impregnating agent, and furthermore, it has excellent heat resistance and intoxication resistance, so it can be used in various applications even as a polymer. It is expected that it will have many uses.

The present invention will be explained below with reference to Examples.

Example 1 2.5 t of anhydrous xylene and 400 liters of sodium were placed in a 5 t three-hole flask, heated to the boiling point of xylene under a nitrogen gas flow, and dimethyldichlorosilane It was added dropwise over 1 hour. After the dropwise addition was completed, the mixture was heated under reflux for 10 hours to form a precipitate. This precipitate was filtered and washed first with methanol and then with water to obtain a white powder of polydimethylsilane 7420.
I got 1.

To this polydimethylsilane 2502, 759v of /phenylonchlorosilane and 1242% of boric acid were heated at a temperature of 100 to 120°C in n-butyl ni-chill under a nitrogen gas atmosphere, and the resulting white resinous material was further vacuum-treated. Middle school 40
Polyborodiphenylsiloxane 0,1259 obtained by heating at 0'O for 1 hour was added and mixed, and the mixture was heated at 820 °C under a nitrogen stream in a 2t quartz tube equipped with a reflux tube.
The organosilicon polymer compound of the present invention is obtained by heating to 0 and polymerizing for 8 hours.

I got it. After cooling at room temperature, add n-hexane and take out as a solution, evaporate L,''-hexane, and obtain ``280''
Concentration in vacuo to O gave 842 solids.

This substance is soluble in benzene, and Hiraga J Molecular Lid 960
, and the hardness viscosity was 0.02. Furthermore, as a result of firing in a nitrogen gas atmosphere up to 1300°C at a heating rate of 5'C/min, the residual rate was 45%.

Example 2 Polyborodiphenylsiloxane 10% was added to 250V of polydimethylsilane synthesized in Example 1. 65% of was added and mixed and heated to 870°C in a nitrogen stream using the same equipment as in Example 1.
Polymerization was carried out for 5 hours to obtain an organosilicon polymer compound of the present invention. Cooled L n-hexane was added to the mixture at room temperature and taken out as a solution, and the n-hexane was evaporated to obtain 176f as a solid. This substance is soluble in benzene and has an average molecular iii'
1720, and the intrinsic viscosity was 0.04. Furthermore, as a result of firing in a nitrogen gas atmosphere to 1800°C at a heating rate of 5°O/min, the residual rate was 79%.

Example 3 Polysila 72509, in which the 2- side chain of Si is a phenyl group and the remaining @ chain is a methyl group, was treated with the 4-lion synthesized in Example 1.
8.0fvI of rosophenylsiloxane was added and mixed, heated at 360°C in a nitrogen stream at the same temperature as in Example 1,
Polymerization was carried out for 7 hours to obtain an organosilicon polymer compound of the present invention. Let it cool at room temperature, add the middle san to the bowl, take it out as a liquid, and let the middle san tJI go to the bottom! 139 solids were obtained. This substance is soluble in benzene, average molecular @a, i
oo, and the intrinsic viscosity was 0.06. Furthermore, as a result of firing in a nitrogen gas atmosphere at a temperature increase of 5°C/min up to 1300'C, the residual rate was 88-.

Ratio of structural units in organosilicon polymerized compounds obtained in each of the above practical examples 1 to 3, (A):
(#) was measured by NMR spectrum, and the results shown in Table 2 below were obtained.

Table 2

[Brief explanation of the drawing]

Figure 1 shows the 4 Ricards of the present invention? 1 of the equipment that synthesizes silane
In the figure, a is a heating furnace, b is a Fi reflux device, 6 is a reaction vessel, and a difJ inert gas inlet; The spectrum (KBr tablet method) is shown. (Volunteer to write procedural amendments) February 17, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 2 Name of the invention Polycarbosilane containing a portion of siloxane bonds 3 Relationship with the person making the amendment Patent applicant address Kashima District, Ibaraki Prefecture Asahimura Oaza Shikata Yamano 873-3
Name Special Inorganic Materials Research Institute 5 Date of amendment order None 7 Contents of amendment Engraving of drawings (no change in content)

Claims (1)

[Claims] It mainly consists of the structural elements of queens (A) and (B), (A): R1-8i-CH, - R1 1): Rs 5i-0-4 (Rm, Rm -Rs and R, Fi each independent K
Represents CH1%C1M1, C・HI or H) (A)
The ratio of (J?) is 5:1 to 200:t, the number average molecular weight is SOO~l000, and the intrinsic viscosity is α01-
140, and is characterized by excellent heat resistance and oxidation resistance, and a high firing residue rate in a non-oxidizing atmosphere.